Weekly Drain and Replinish
Topping Off the Tank's Reservoir
I really do own 14 books on Hydroponic Indoor Growing. And I have studied them too. Some of the books were written simply, and some are difficult for me to comprehend and even more difficult for me to explain. They all vary a little on the perfect pH level, and they all vary on LIGHTING, some books were written way before CFLs were sold, or when CFLs were new on the scene. But they all agree on Topping Off the tank and Draining and Replinishing the water and nutrients.
To address this, I am going to post it twice to be sure I explain it. You will need to read both explanations.
After the nutes are added to the tank and the pH is balanced, the plants start eating, consuming the food. Logically, the larger the tank, the more water there is, and the more nutes you need. Logically, the larger the plants, the more they will eat from the tank. Logically, the more plants that are in the tank, the more they will eat. And Logically, the more they eat, the more nutes that you need in the tank. The amount of nutes provided is in relationship to the amount of water, NOT the amount of plants. It is the Ratio or Proprotion in the water that is important. The amount of nutes added to the tank are measured by we commonly call a PPM Meter, PPM meaning parts per million.
The Instructions on the nutrients contain the proper amount of nutes to add to the water, usually determined by "per gallon", and not by "per plant" or "size of plants". In the beginning, we start with 1/4 dose of nutrients, because a full dose is meant for full grown plants. If we use a ppm meter, we seek a ppm of 150 to 250 ppms on average for small young sprouts, it varies from nutrient to nutrient. As the plants grow, we then slowly and gradually increase the nutrients fed to them, and consequently we increase the ppm. By the time the plants are over a foot tall, we will be in the neighborhood of a ppm of 600, then 800 on up to 1200 ppm. Some growers risk even higher ppms, watching the leaves tips for yellowing, to know when to back off with feedings. And as we add more food, the plants grow and eat more, indicated by them also drinking more water. As a rule of thumb, we figure if they drank half of the water, they then must of ate half the food. That is close to being right, but not precisely. If the grow room was exceptionly HOT, they can drink more water without eating more food. And consequently, some days, they eat more, some days they eat less, regardless of the amount of the water missing.
As they eat, they do not eat all of the delivered nutes at the same rate, or same proportion, and that changes the pH and the ppm. It also changes what they call the RNC, or RELATIONSHIP OF NUTRIENT CONCENTRATION. That CHANGE is not easy to calculate or measure, like the ppm or pH is easy to measure.
When the nutrients are first introduced or added, the RNC is perfect, or properly proportioned. In other words, there are specific amounts or precise amounts of each needed nutrient. The exact amount of needed Nitrogen, Phosphorous, and Potash, also commonly called Potassium are present and available for food for the plants.
BUT, as the plants eat, they do not eat all of the nutrients in a perfect proportion or at a perfect rate or equal rate. Some days, they want what grows longer roots, some days, they want what makes more leaves. The plants actually nibble at some nutrients in the mix each day, and gobble down some others. Some of the nutrients are not hardly eaten at all, some are absorbed very quickly. This creates an IMBALANCE of the mix. If you add more water and nutes daily to replace the eaten nutes, (CALLED TOPPING OFF) the IMBALANCE INCREASES. If you only add plain water daily, again, Top It Off, you still get the imbalance. AND the nutes not eaten, or the nutes that are increased daily cause a build up of nutes, and that creates a BAD imbalance of the RNC.
When this happens, the water becomes TOXIC and unusable even tho the ppm meter says there is a proper amount of nutrients. The plants say I AM NOT HAPPY WITH THE BUFFET and like a spoiled child unhappy at the dinner table, they suddenly refuse to eat anything. This is called NUTRITIONAL LOCKOUT. This happens even tho the ppm meter says there are plenty of parts per million in the water. The ppm meter does not indicate if the nutrients are balanced or at a toxic level. It just indicates there is plenty of food on the table.
THIS IS WHY WE MUST WEEKLY DUMP IT ALL AND START ALL OVER.
THIS IS WHY WE MUST DRAIN AND REPLINISH WEEKLY, regardless of whether we TOP OFF with plain water, or TOP OFF with water and a fractional dose of nutes.
Changing the water weekly maintains the proper RNC.
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